Method for Signaling a Brake Process at a Trailer Vehicle, Control Device for this Purpose and Dynamo System, Trailer Vehicle Brake System and Trailer Vehicle with Said Control Device

ABSTRACT

The invention relates to a method for signalling a braking process at a trailer vehicle ( 2 ), wherein according to the invention a control device ( 9 ) which is arranged on the trailer vehicle ( 2 ) determines at least one braking value A which is assigned to the braking process, and actuates at least one brake light ( 19 ), arranged on the trailer vehicle ( 2 ), as a function of said braking value A in such a way that depending on this braking value A at the trailer vehicle ( 2 ) the braking process is signalled differently compared to signalling in the case of at least one other braking value A which can be determined by this control input ( 9 ) during a braking process. As a result, traffic following the trailer vehicle ( 2 ) and/or an emergency braking situation can be signalled and therefore safety in road traffic can be increased. In addition, the invention relates to the control device ( 9 ) for carrying out the method and to a dynamo system and to a trailer vehicle braking system which each have this control device ( 9 ), and to a trailer vehicle ( 2 ) which has the control device ( 9 ) or this dynamo system and/or trailer vehicle brake system.

The invention relates to a method for signaling a braking process at a trailer vehicle. In addition, the invention relates to a control device for the trailer vehicle, by means of which control device the method can be carried out and/or controlled. Furthermore, the invention relates to a light system having this control device, to a trailer vehicle brake installation having this control device and finally to a trailer vehicle which has this control device and/or this light system and/or this brake system and/or devices by means of which the method according to the invention can be carried out.

The invention is provided, in particular, for trailer vehicles which can be braked in an electronically open-loop or closed-loop controlled fashion by means of an electronic brake system (EBS). Electronic brake systems are usually used in vehicles, in particular utility vehicles, such as trucks, and have, inter alia, the function of controlling brake cylinders or other brake application devices of a service brake installation of the vehicle at all the axles of the vehicle when a brake pedal is activated, in such a way that brakes to which the brake cylinders are assigned respond simultaneously and uniformly. With electronic brake systems it is possible to shorten a braking distance of the vehicle and at the same time achieve uniform wear of brake linings. The electronic brake system actuates here the pneumatically operating brake cylinders or service brake devices electronically. Flow times for a buildup of pressure or reduction in pressure are reduced and reaction times of the brake system are shortened in this context.

Known electronically closed-loop controlled brake systems, cf. Bosch, Kraftfahrtechnisches Taschenbuch [Bosch automotive manual], 26^(th) edition, page 904, comprise a control device and pressure controlling modules which are connected in a signal-transmitting fashion to the control device and to which brake devices of the vehicle are assigned. In this context, it is possible to arrange an individual control unit or a plurality of control units in a decentralized fashion. If an input signal relating to a braking request is present at the control unit, the pneumatic control pressures which are present at a control pressure line which conducts a redundancy pressure are shut off in the pressure controlling modules. The electronic control unit determines a brake setpoint pressure as a function of a deceleration request and further vehicle parameters. This brake setpoint pressure is transmitted to the brake controlling modules. The brake controlling modules apply the brake setpoint pressure to the brake cylinders on an axle basis or wheel basis.

For trailer vehicles, trailer control modules are known, cf. Bosch, automotive manual, 26^(th) edition, page 906, which permit the trailer control pressure to be controlled in accordance with the functional requirements of the electronic brake system. A method for operating an electronically controlled pressure medium brake installation is known, for example, from DE 101 56 673 A1.

In addition, both known towing vehicles and known trailer vehicles have light systems by means of which a braking process can be signaled. Brake lights of the light system of the trailer vehicle are actuated here as brake lights of the towing vehicle. An electrical connection which is necessary for this purpose is made by means of a standardized, and to that extent obligatory, plug-type connection according to ISO 12098 between the towing vehicle and the trailer vehicle.

In order to inform traffic following the vehicle about the severity of a braking operation, an adaptive brake light or the modulation of an emergency brake light is known for towing vehicles. In this case, the control unit of the electronically closed-loop controlled brake installation in the towing vehicle carries out an emergency braking evaluation, wherein available vehicle para meters are evaluated and in response thereto it is decided whether an emergency braking situation is present. This rules out the possibility of hazardous situations arising for the following car traffic as a result of incorrect indication of emergency braking of the towing vehicle. If an emergency braking situation is detected, it is displayed by means of the adaptive brake light or the emergency brake light of the towing vehicle and the following traffic is correspondingly informed or warned about the severity of the braking operation.

However, if the towing vehicle tows a trailer vehicle, in particular a semitrailer or drawbar trailer, the emergency brake light on the towing vehicle for indicating emergency braking to the following traffic cannot be seen since it is covered by the trailer vehicle. In emergency braking situations of vehicle trains which have the towing vehicle and at least one trailer vehicle, hazardous traffic situations may therefore occur even if the towing vehicle is equipped with an adaptive brake light. It is not possible to couple a brake light on the trailer vehicle to the adaptive brake light or the emergency brake light of the towing vehicle since the abovementioned plug-type connection according to ISO 12098 between the towing vehicle and the trailer vehicle does not provide the necessary connection facility.

DE 10 2007 054 189 A1 discloses a brake control module for a trailer vehicle which actuates warning lamps and/or brake lights of a trailer vehicle which has this brake control module. For this purpose, the brake control module is actuated by the towing vehicle via a towing vehicle-warning lamp interface which is provided for this purpose. A disadvantage of this actuation process is that it therefore requires specific interfaces to be provided both on the towing vehicle and on the trailer vehicle, which interfaces do not correspond to the standard. As a result, trailer vehicles which have a brake control module according to DE 10 2007 054 189 A1 are not able to be coupled to towing vehicles with standardized interfaces and operated therewith. Furthermore, although the brake lights of the trailer vehicle are actuated by this known brake control module, additional actuation of an adaptive brake light or of an emergency brake light by this brake control module is not provided and/or does not appear possible without once more expanding the interfaces between the towing vehicle and the trailer vehicle. The following traffic is therefore not informed about an emergency braking operation either.

The invention is therefore based on the problem of improving safety in road traffic during operation of a trailer vehicle, in particular with an electronic brake system.

The invention solves this problem with a method as claimed in claim 1, with a control device as claimed in claim 6, with a light system as claimed in claim 11, with a trailer vehicle brake installation as claimed in claim 13 and with a trailer vehicle as claimed in claim 14.

In particular, the invention solves the problem in that data and/or signals which are available at the trailer vehicle are evaluated by a control device which is also arranged on the trailer vehicle, which data and/or signals permit conclusions to be drawn about a braking process, in particular about a severity level and/or other characteristic features of the braking process such as an automatic braking intervention. In response to this, in particular in the case of a detected emergency braking operation and/or in the case of a detected automatic braking intervention, the control device actuates at least one existing or additional brake light of the trailer vehicle in such a way that the following traffic can draw conclusions about the braking process, in particular about the severity or other features of the braking process, and, for example, detects an emergency braking operation as such, from the lighting up of the brake lights.

The actuation of the brake lights is therefore not carried out by the towing vehicle and not carried out by means of control instructions which are received from the towing vehicle. Instead, the control device at the trailer vehicle decides automatically whether, for example, an emergency braking operation is present and said control device correspondingly actuates the brake lights with the result that the following traffic is warned. There is no need to provide any additional interfaces between the towing vehicle and the trailer vehicle for this purpose. In trailer vehicles which are equipped according to the invention, the method according to the invention can therefore be carried out in conjunction with any towing vehicle which has a standardized interface and, in particular, an electronic brake system and is equipped to tow a trailer vehicle which can be operated with an electronic brake system.

In particular, according to an embodiment of the inventive method the control device which is arranged on the trailer vehicle determines at least one braking value which is assigned to the braking process, in particular represents a severity level of the braking process or other features which characterize the braking process. For this purpose, the control device has braking value determining means. In addition, the control device has brake light actuation means. The control device and in particular the brake light actuation means actuate at least one brake light of the light system as a function of this braking value in such a way that depending on this braking value the braking process is signaled differently at the trailer vehicle compared to a signaling operation in the case of at least one other braking value which can be determined by this control device during a braking process. A severity level of this braking process which is assigned to the respective braking process or the braking value can be here a selected or determined deceleration of the trailer vehicle or of a towing vehicle towing the trailer vehicle or of a vehicle train having the trailer vehicle and the towing vehicle. The control device preferably has an emergency brake signal output by means of which the light system can be actuated.

The control device is preferably at the same time a control center of an electronic brake system at the trailer vehicle and in addition to controlling the brake light or the emergency brake signaling operation it also controls this electronic brake system at the trailer vehicle. As a result, control functions for the brake light and/or for the emergency brake signaling operation are integrated into the control center of the electronic brake system which is present in any case at the trailer vehicle. This is advantageous, in particular, because in this control center there are the signals and/or data which are advantageously extracted for open-loop and/or closed-loop control functions of the electronic brake system. These signals and/or data can be used at least partially, if appropriate together with further input variables for detecting particular brake situations, in particular an emergency braking operation, for actuating the brake light or emergency brake signaling operation.

The control device preferably has receiver means by means of which it receives data and/or signals transmitted from a towing vehicle towing the trailer vehicle to the trailer vehicle via a databus, in particular controller area network (CAN) databus. These data and/or signals are used by the control device to determine the braking value. Alternatively or additionally, the control device uses signals and/or data to determine the braking value which are received from devices at the trailer vehicle, for example from sensors.

The control device preferably actuates the brake light via a databus. The brake light actuation means are embodied appropriately for this purpose. The control device is therefore connected via a databus to a device of a light system of the trailer vehicle, which device in turn actuates the brake lights.

The control device preferably switches, or the brake light actuation means preferably switch, an output stage which actuates the brake light. Actuation can be carried out directly or indirectly here, for example by means of a relay. After the output stage has been actuated, for example via the abovementioned databus, the currents which are required to actuate the brake light can therefore be made available by the output stage. The control device can therefore be configured for comparatively low currents.

The brake light actuation means are preferably embodied in such a way that the control device actuates the brake light, in particular an emergency brake light, via optical cabling via which this brake light is also actuated by the towing vehicle. Optical cabling for actuating the brake light or an emergency brake light is therefore integrated into the existing optical cabling at the trailer vehicle. This saves costs since there is no need for any, in particular complete, additional optical cabling to be provided for the invention.

The control device is preferably embodied in such a way that it uses one or more variables, in particular data and/or signals, to determine the braking value, which variables are determined at the towing vehicle or at the trailer vehicle for the towing vehicle, for the trailer vehicle or for a vehicle train having the towing vehicle and the trailer vehicle.

The invention preferably uses at least one actual speed, particularly preferably at least two actual speeds, as such a variable here. Alternatively or additionally, the invention uses at least one actual deceleration as a variable. Both the actual speed and the actual deceleration may be an estimated or measured variable. For example, wheel sensors measure actual speeds at wheels of the trailer vehicle and determine a decrease in the speed through comparison of actual speeds which are determined at various times, or actual speeds at different wheels are compared with one another and hazardous driving situations which require an automatic braking intervention are determined in the process. In such situations it may be appropriate to output an emergency brake signal.

Further variables of this type, which are used as an alternative or in addition to the determination of the braking value, are at least one setpoint deceleration and/or at least one braking request signal. One of these two variables is preferably transmitted to the trailer vehicle from the towing vehicle. The setpoint deceleration may be a variable which is calculated or determined by using the brake request signal.

Alternatively or additionally, a variable which is used to determine the braking value is an information item relating to an automatic braking intervention, in particular by the trailer vehicle. This information may be, for example, a dimension variable which brings about the braking intervention. Alternatively, the information may also be a variable which is influenced in response to an automatic braking intervention or indirectly by the automatic braking intervention. Variables which are used to determine the braking value may be acquired from interventions by functions of the control device, such as, for example, functions of an anti-lock brake system (ABS), a traction control system or an electronic stability program (ESP).

Alternatively or additionally, information relating to what is referred to as an RSS braking operation, i.e. a braking operation using a roll stability support (RSS) system or a system which counteracts lateral tilting, is preferably used to determine the braking value, wherein in the case of a detected RSS braking operation, in particular at the trailer vehicle, or in the case of another automatic braking intervention an emergency braking operation is signaled and/or the braking process is signaled differently compared to a braking operation without RSS deployment or automatic braking intervention. In particular, the brake light or emergency brake light signals an emergency braking operation or hazardous situation in response to the automatic braking intervention at the trailer vehicle by means of the RSS system. In response to the automatic braking intervention, a braking value is in fact determined which in turn brings about actuation of the brake light in order to signal the emergency braking operation.

Information which is used to determine the braking value can also be vehicle data such as wheel speeds, load state information and sensor data of a sensed lateral acceleration. The load state information may be, for example, determined by means of a load sensor or by means of braking processes or input manually. All this information may be used alone or together even without RSS deployment in order to determine the braking value. In particular, the invention alternatively or additionally directly uses at least one variable which is sensed at the trailer vehicle, at the towing vehicle or at the vehicle train or sensor signals or sensor data, for example of a sensed lateral acceleration, as variables for determining the braking value or a plurality of braking values.

The control device preferably actuates the brake light adaptively in accordance with the respective braking value. In particular, an additional emergency brake light of the light system at the trailer vehicle, but alternatively also a brake light which is used during a normal braking operation, is actuated adaptively by the control device. As a result, the following traffic is at least informed that an emergency braking operation is occurring. If appropriate, the following traffic is additionally informed about the severity of the emergency braking operation. For example, the brake light can alternately light up with a frequency as a function of the respective braking value and not light up again or light up with a different luminosity.

The control device preferably has emergency braking detection means by means of which it compares a braking value with a limiting value. The limiting value may be a predetermined or determinable or settable limiting value. The control device preferably has a memory in which the limiting value or a plurality of limiting values are stored. The control device detects, or the emergency braking detection means of the control device detect, the respective braking process as an emergency braking operation in response to it being detected that the limiting value is reached, exceeded or undershot. In response to a detected emergency braking operation, an emergency brake signal is generated and is made available via an emergency brake signal output, in particular an output stage which is connected upstream of the brake light. A braking process which is detected as an emergency braking operation is signaled differently, in particular through actuation of the emergency brake light or through the emergency brake signaling operation, than a braking process which is not detected as an emergency braking operation. If appropriate, this braking process which is detected as an emergency braking operation is also signaled differently than another braking process which is also detected as an emergency braking operation, and during which another braking value was, however, determined and another limiting value was not reached, was reached or was exceeded.

The brake light actuation means are preferably embodied in such a way that the braking process is signaled compared to another braking value which can be determined during a braking process by one or more of the following functions, in particular when the braking process is detected as an emergency braking operation.

Such a function is preferably lighting up the brake light more brightly, wherein the brake light can be a normal brake light by means of which comparatively weak braking can also be signaled.

The braking process is preferably alternatively or additionally signaled by actuating and fighting up at least one additional brake light, in particular emergency brake light. This brake light can, if appropriate, also light up with differing degrees of brightness depending on the braking value which is determined. The emergency brake light is, for example, designed to emit an adaptive brake light.

In one advantageous embodiment, the braking process is alternatively or additionally signaled by cyclically lighting up the brake light or emergency brake light. For this purpose, the brake light is preferably actuated in such a way that this brake light automatically switches a lighting means, such as at least one filament light and/or LED, on and off in an alternating fashion and/or is energized alternately and interrupts an electric line. For this purpose, the brake light has suitable switching means such as, for example, a relay and/or an electronic circuit.

In a further advantageous embodiment, the braking process is alternatively or additionally signaled by cyclically actuating the existing and/or additional brake light or emergency brake light. The cyclical actuation is carried out here with a fixed or variable frequency, wherein the frequency can be set manually or automatically. For example, the frequency can be set automatically as a function of the braking value which is determined.

The control device preferably switches a relay by means of which actuation of the brake light can be interrupted by the towing vehicle continuously or cyclically for a finite time period or can be switched over to another actuation operation. For example, during an emergency braking operation a brake light is not actuated by the towing vehicle but rather by the control device in order to be able to allow this brake light to light up more brightly. In the case of the cyclical interruption of the actuation by the towing vehicle, the brake light may, for example, not be lit up during these interruptions or may be actuated by the control device of the trailer vehicle in a different way or in such a way that it lights up more brightly or more darkly than usual during these interruptions.

The control device advantageously has means, for example hardware components and/or software components, for carrying out steps of the method according to embodiments of the invention for signaling a braking process.

The light system according to the invention is provided for signaling a braking process at a trailer vehicle having this light system. The light system has at least one brake light and a control device according to the invention, by means of which this brake light can be actuated.

The light system preferably has a databus by means of which signals and/or data can be transmitted from a towing vehicle towing the trailer vehicle to said trailer vehicle.

The light system preferably also has an output stage by means of which the brake light can be actuated directly or indirectly.

The light system preferably also has optical cabling via which the brake light can be actuated both from the towing vehicle and from the control device.

The trailer vehicle brake installation according to the invention has an electronic brake system (EBS) and a control device according to the invention. In addition, the trailer vehicle brake installation has at least one brake activation control module which is connected in a signal-transmitting fashion to the control device. The brake activation control module is, for example, a valve device or a modulator by means of which a pneumatic or hydraulic pressure can be controlled.

In addition, the trailer vehicle brake installation has at least one brake activation device which is connected electrically, pneumatically or hydraulically to the brake activation control module and by means of which at least one wheel, assigned to this brake activation device, of a trailer vehicle having the trailer vehicle brake installation can be braked in response to at least one electrical signal received at the control device. The brake activation device may be here, for example, a brake cylinder which can be activated pneumatically or hydraulically. Alternatively, the brake activation device can, however, also be an actuator of a brake which can be activated electrically.

The trailer vehicle brake installation advantageously has an interface with the databus between the towing vehicle and the trailer vehicle, with the result that signals or data are transmitted by the towing vehicle through the databus, via the interface with the control device of the trailer vehicle, and are used there both for actuating the brake activation device and for the detection of emergency braking and/or the determination of the braking value A and signaling of the respective braking process.

Further advantageous embodiments can be found in the claims and in the exemplary embodiments which are explained in more detail with reference to the drawings, in which:

FIG. 1 shows a pneumatic and electrical circuit diagram of a brake installation having an electronically closed-loop controlled brake system (EBS), and

FIG. 2 shows a schematic flowchart of an emergency braking signal function of an electronically closed-loop controlled brake system of a trailer vehicle according to FIG. 1.

FIG. 1 shows a pneumatic and electrical circuit diagram of a brake installation having an electronic brake system (EBS) in a vehicle train composed of a towing vehicle 1 and trailer vehicle 2. The electrical lines of the electronic brake system are shown with thicker lines than the pressure medium lines, in particular pneumatic and/or hydraulic lines, in the circuit diagram.

All the wheels 3 both of the towing vehicle 1 and the trailer vehicle 2 are respectively assigned a brake cylinder 4, as a brake activation device, which is activated by a pressure medium and is operated, in particular, pneumatically or hydraulically. Pressure medium containers 5, in particular compressed air containers, are provided both in the towing vehicle 1 and in the trailer vehicle 2 in order to supply the brake cylinders 4.

The pressure medium activation, in particular pneumatic or hydraulic activation, of the brake cylinders 4 is carried out by means of pressure closed-loop control modules 6, 7 which are each connected in a signal-transmitting fashion to a control device or a control unit 8, 9 via a brake CAN (CAN=Controller Area Network) bus 10. In the towing vehicle 1, the wheels 3 are each assigned 1-channel pressure closed-loop control modules 6. A brake activation control module or 2-channel pressure closed-loop control module 7, which supplies the brake cylinders 4 of all the wheels 3, is provided in the brake system of the trailer vehicle 2. However, it is also possible to assign separate pressure closed-loop control modules on a wheel basis or axle basis to each wheel 3 for the trailer vehicle 2.

A service brake valve 13 is connected as a signal generator to the brake installation which can be activated by pressure medium and is, in particular, a pneumatic and/or hydraulic brake installation, the accelerator pedal of which can be activated by the driver of the towing vehicle. When the accelerator pedal moves, a signal is generated which represents a braking request, and said signal is input into the control unit 8 of the towing vehicle 1. The pneumatic devices of the trailer vehicle 2 are connected to the towing vehicle 1 via a trailer control valve 14 which, on the one hand, is connected via a supply coupling head 15 to a trailer brake valve 16 and to a downstream pressure container 5 of the trailer vehicle 2. On the other hand, the trailer control valve 14 is connected via a brake coupling head 17 to the control unit 9 of the brake installation in the trailer vehicle 2.

When the service brake valve 13 is activated, the control unit 8 in the towing vehicle calculates the braking request of the driver, wherein at the same time backup actuating devices which are provided in the pressure closed-loop control modules 6 are activated and the pneumatic control pressures are shut off. The control unit 8 calculates, as a function of the braking request and available operating variables such as vehicle mass and instantaneous operating load, the setpoint braking pressure which is predefined to the pressure closed-loop control modules 6 via the respective brake CAN bus 10.

The trailer vehicle 2 has a separate electronic brake system which comprises a control unit as a central control device. The control unit 9 of the trailer vehicle 2 determines the setpoint braking pressure for the connected pressure closed-loop control module 7 on the basis of the input signals for said trailer vehicle 2. In this context, the input signal which represents a braking request is predefined by the control unit 8 of the towing vehicle. The control units 8, 9 of the towing vehicle 1 and/or of the trailer vehicle 2 are connected to one another for this purpose via a trailer CAN bus 18 according to ISO 11992. The control unit 9 calculates, as a function of the detected braking request and/or other available operating variables, the setpoint braking pressure for the brake cylinders 4, which setpoint braking pressure is predefined to the pressure closed-loop control module 7 via the brake CAN bus 10.

In the case of vehicle trains which do not have a data interface ISO 11992, another available variable for representing the braking request can be predefined to the control unit 9 of the trailer vehicle instead of the predefined setpoint value from the towing vehicle. The setpoint value can be predefined, for example, by a pressure sensor of the trailer control valve 14 which measures the control pressure for the trailer vehicle. Alternatively, the setpoint value can also be specified by pressure sensors arranged to a trailer vehicle.

A service brake lighting system on the rear side of the trailer vehicle 2 in the direction of travel of the vehicle train is coupled via a plug-type connection (not illustrated) according to ISO 12098 to the lighting system of the towing vehicle 1, with the result that lighting up of the brake lights of the towing vehicle 1 is connected through to the trailer vehicle 2.

The control unit 9 in the trailer vehicle 2 determines at least one braking value assigned to the respective braking process and compares said braking value with a limiting value stored in a memory of the control unit 9. As a result, the control unit 9 carries out, in particular, an emergency braking detection process and causes an emergency braking signal function to be activated if an emergency braking situation is detected. In this context, an emergency brake light 19 is switched on in order to indicate, on the rear side of the trailer vehicle 2, the emergency braking situation to the following traffic by lighting up the brake light 19. In this case, an emergency braking signal output 20 of the control unit 9 is connected to an energy source, in the present exemplary embodiment an output stage 21, via a control line 22. The output stage 21 outputs a corresponding electrical signal for the emergency brake light 19 when actuation is carried out by the control unit 9 with an emergency braking signal.

Flashing of the emergency brake light 19 can be set by correspondingly changing the parameterization of the control unit 9.

In the exemplary embodiment shown, a relay 23, which ensures that the emergency brake light 19 flashes, is arranged between the output stage 21 and the emergency brake light 19. The relay 23 can, if appropriate, be switched via a databus (not illustrated) or via a further control line from the control unit 9. The output stage 21 actuates the emergency brake light 19 via the relay 23. The output stage 21 and the relay 23 therefore form an emergency brake circuit 24 which is connected to the brake system via the control unit 9, and switches on the emergency brake light 19 when an emergency braking situation is detected.

The emergency brake light 19 for indicating the emergency braking situation is provided as a separate brake light, in addition to the operational lighting system of the trailer vehicle 2 on the rear side thereof. Alternatively, it is also conceivable to actuate the service brake lighting system of the trailer vehicle 2 by means of the emergency brake circuit 24, or the actuation of the emergency brake light 19 is integrated into the service brake lighting system. In particular, the emergency brake light 19 can be a brake light which, during every normal braking process, is actuated by the usual service brake lighting system via the plug-type connection (not illustrated) according to ISO 12 098 and an electrical line from this plug-type connection to the relay 23, wherein the output stage 21 can be dispensed with and/or is arranged in the towing vehicle. However, it is alternatively also possible to provide a control line via which the service brake lighting system actuates the output stage 21.

In these alternative embodiments, the relay 23 can be switched via the control line 22 which connects the controller 9 to the relay 23 in these cases and/or via another control line (not illustrated). The control line 22 and/or this other control line is preferably embodied as a bus connection via which control data for switching the relay are transmitted. The relay 23 interrupts the actuation of the emergency brake light 19 by the service brake lighting system cyclically or for as long as an emergency braking situation is present. Actuation of the emergency brake light 19 and/or of a usual brake light is interrupted here or the actuation shown in FIG. 1 is switched over to. If appropriate, two relays are also provided here, wherein one relay (not illustrated) performs the switching over and the relay 23 ensures that the flashing occurs.

In order to detect an emergency braking situation, the control unit evaluates the internal available operating parameters of the vehicle. In this context, in addition to an input signal, which represents a braking request and is present via the CAN bus 18, the speed of the trailer vehicle and/or the actual or desired deceleration of the vehicle are used. When predefined limiting values are reached, the control unit 9 detects an emergency braking situation and activates the emergency braking signal function.

The brake light 19 for indicating the emergency braking situation is embodied as an adaptive brake light 19 and is actuated adaptively by the brake system on the basis of the evaluation of the variables taken into account. In this context, different signals are programmed in the control unit 9 depending on the intensity of the braking and/or braking deceleration.

The control unit 9 has means for comparing variables with comparison variables and/or at least one limiting value. These variables which are to be used for comparison may comprise one or more variables which are taken into account for determination of the setpoint braking pressure in the brake system. Variables which are to be used for the emergency braking detection and the emergency braking signal function which is implemented in the control unit are, in particular, the speed of the trailer vehicle 2, of the towing vehicle 1 or of the vehicle train and/or the actual or desired deceleration of the trailer vehicle 2, of the towing vehicle 1 or of the vehicle train. These variables are at least partially obtained from the towing vehicle 1 via the CAN bus 18 for the determination of the setpoint pressure for the brake system and/or acquired from the measured values of the measuring sensors on the trailer vehicle, for example the rotational speed sensors 11.

Further variables which can be used for the emergency braking signal function can be acquired from interventions via other functions of the control unit, such as for example anti-lock brake systems (ABS), traction control systems (TCS) or electronic stability programs (ESP). The static friction of the roadway, the measured values of the brake wear meters 12 or else the load of the vehicle or the load state can also be evaluated in the control unit for the determination of an emergency braking situation and activation of the emergency braking signal function. In addition, vehicle data such as wheel speed, load data and/or data and/or measured values relating to a lateral acceleration which are determined by means of a sensor integrated, in particular, into the control unit 9 and which are used for a tilting stability device or a roll stability support (RSS) may be employed as variables for the detection of the emergency braking.

In order to compare the operating variables used during the detection of emergency braking with predefined limiting values and to activate the emergency braking signal function when the predefined limiting values are exceeded, limiting values for the variables to be taken into account are stored in a memory 25 of the control unit 9.

FIG. 2 shows, in a schematic flowchart, a method of operation of the control unit with the emergency braking signal function implemented therein. A step 26 serves to acquire input values from received signals or data and to process said values, wherein a setpoint braking pressure 8 and at least one braking value A are determined. A signal which is received in such a way is the input signal 27 which represents the braking request and/or a setpoint deceleration. The input signal 27 is predefined to the control unit in the exemplary embodiment according to FIG. 1 via the control unit 8 of the towing vehicle. On the other hand, operating parameters 28 are acquired, in particular from the measured value generators of the trailer vehicle, and are fed to the control unit in signals or data.

A plurality of these acquired input values or all the acquired input values and/or values determined from a number of these input values or from all of these input values are evaluated and used as the basis for the determination of the setpoint braking pressure P for the trailer vehicle or for the determination of another variable according to which the brakes on the trailer vehicle are activated. Such input signals, which are used to determine the setpoint braking pressure P, can be, for example, a vehicle deceleration or an actual deceleration determined for the trailer vehicle, towing vehicle or vehicle train and/or the speed of the trailer vehicle.

At least one variable, which is one of the input signals 27 or 28 or a variable determined from at least one of these variables 27, 28, is used to determine the at least one braking value A or as a braking value A for the realization of the emergency braking signal function according to the invention. This braking value A is compared with at least one predefined limiting value G in a comparison step 31. If the braking value and/or one of the operating variables 29 which are used for the emergency braking signal function reaches or exceeds a limiting value G which is provided for it or them, the emergency braking signal function 33 is activated. In this context, a plurality of limiting values G can be provided for each braking value A which is used. A corresponding emergency braking signal is predefined here to each of the limiting values G, with the result that the severity of the emergency braking operation of the trailer vehicle 2 can be indicated to the following traffic by means of the emergency brake light 19 (FIG. 1).

Hitherto it was impossible to actuate an adaptive brake light on the trailer vehicle by means of the electronic brake system of towing vehicles since the standardized, and to this extent obligatory, plug-type connections between the towing vehicle 1 and the trailer vehicle 2 did not permit such a transmission, but now by virtue of the control of an adaptive brake light 19 by the electronic brake system of the trailer vehicle 2 it is possible to indicate the emergency braking situation to the following traffic.

All the features specified in the description above and in the claims are capable of being used either individually or in any desired combination with one another. The disclosure of the invention is therefore not restricted to the described or claimed feature combinations. Instead, all feature combinations are to be considered as being disclosed. 

1. A method for signaling a braking process at a trailer vehicle (2), characterized in that a control device (9) which is arranged on the trailer vehicle (2) determines at least one braking value (A) which is assigned to the braking process, and actuates at least one brake light (19), arranged on the trailer vehicle (2), as a function of this braking value (A) in such a way that depending on this braking value (A) the braking process is signaled differently at the trailer vehicle (2) compared to a signaling operation in the case of at least one other braking value (A) which can be determined by this control device (9) during a braking process.
 2. The method as claimed in claim 1, characterized in that the control device (9) additionally also controls an electronic brake system at the trailer vehicle (2), in order to determine the braking value (A) receives signals or data (27) which are transmitted from a towing vehicle (1) towing the trailer vehicle (2) to the trailer vehicle (2) via a databus (18), and actuates the brake light (19) via a databus and/or switches an output stage (21) which actuates the brake light (19), and/or actuates the brake light (19) via optical cabling via which this brake light (19) is also actuated by the towing vehicle (1).
 3. The method as claimed in claim 1 or 2, characterized in that the control device (9) uses one or more of the following variables to determine the braking value (A): at least one actual speed; at least one actual deceleration; at least one setpoint deceleration (27); at least one braking request signal; at least one variable (29) which is sensed at the trailer vehicle or towing vehicle or vehicle train; and at least one information item relating to an automatic braking intervention by the trailer vehicle.
 4. The method as claimed in one of the preceding claims, characterized in that the control device (9) actuates the brake light (19) adaptively in accordance with the respective braking value (A), wherein the control device (9) compares this braking value (A) with a limiting value (G) and detects the braking process as an emergency braking operation in response to it being detected that the limiting value (G) is reached, exceeded or undershot, wherein the braking process is signaled compared to another braking value (A) which can be determined during a braking process by one or more of the following functions: lighting up the brake light (19) more brightly; actuating and lighting up at least one additional emergency brake light (19) as a brake light; cyclically lighting up the brake light (19), wherein the brake light (19) automatically switches a lighting means of the brake light (19) on and off in an alternating fashion in response to its actuation by the control device (9); cyclically actuating the brake light (19), wherein the control device switches a relay (23) which interrupts actuation of the brake light (19) by the towing vehicle (1) for a finite time period or switches over to another actuation operation.
 5. The method as claimed in one of the preceding claims, characterized in that in response to an automatic braking intervention at the trailer vehicle (2) by a stability system, in particular by a roll stability support (RSS), which counteracts a tendency of the trailer vehicle (2) to tilt laterally, the brake light (19) or emergency brake light at the trailer vehicle (2) signals an emergency braking operation on the basis of the determined braking value and its actuation as a function thereof or the control device (9).
 6. A control device for a trailer vehicle for carrying out the method as claimed in one of claims 1 to 5, characterized by braking value determining means by means of which at least one braking value (A), which is assigned to a braking process, can be determined, and brake light actuation means by means of which at least one brake light (19) of the trailer vehicle (2) can be actuated as a function of this braking value (A) in such a way that depending on this braking value (A) a respective braking process can be signaled differently at the trailer vehicle (2) compared to a signaling operation in the case of at least one other braking value (A) which can be determined by this control device (9) during a braking process.
 7. The control device as claimed in claim 6, characterized in that the control device is a control center of an electronic brake system at the trailer vehicle, and has receiver means by means of which data or signals, which are transmitted from a towing vehicle towing the trailer vehicle to this trailer vehicle via a databus, can be received in order to determine the braking value, and the brake light actuation means are embodied in such a way that the brake light (19) can be actuated via the databus, and/or an output stage (21), by means of which the brake light (19) can be actuated, can be switched, and/or the brake light can be actuated via optical cabling via which this brake light can also be actuated by a towing vehicle (1) towing the trailer vehicle (2).
 8. The control device as claimed in claim 6 or 7, characterized by an embodiment such that the control device can use, in particular uses, one or more of the following variables to determine the braking value: at least one actual speed; at least one actual deceleration; at least one setpoint deceleration (27); at least one braking request signal; at least one variable (28) which is sensed at the trailer vehicle or towing vehicle or vehicle train; and at least one information item relating to an automatic braking intervention by the trailer vehicle.
 9. The control device as claimed in one of claims 6 to 8, characterized in that the control device (9) is embodied in such a way that the brake light (19) can be actuated adaptively by means of the control device (9) in accordance with the respective braking value (A), the control device (9) has emergency braking detection means by means of which the braking value (A) can be compared with a limiting value (G), and the braking process can be detected as an emergency braking operation in response to it being detected that the limiting value (G) is reached, exceeded or undershot, the light system actuation means are embodied in such a way that the braking process can be signaled compared to another braking value (A) which can be determined during a braking process by one or more of the following functions: lighting up the brake light (19) more brightly; actuating and lighting up at least one additional emergency brake light (19) as a brake light; cyclically lighting up the brake light (19), wherein the brake light (19) automatically switches a lighting means of the brake light (19) on and off in an alternating fashion in response to its actuation by the control device (9); cyclically actuating the brake light (19), wherein a relay (23) can be switched by means of the control device (9) in such a way that actuation of the brake light (19) by the towing vehicle (1) can be interrupted for a finite time period or can be switched over to another actuation operation by means of the relay.
 10. The control device as claimed in one of claims 6 to 9, characterized by an embodiment of the control device (9) such that a braking value is determined in response to an automatic braking intervention at the trailer vehicle (2) by a stability system, in particular by a roll stability support (RSS), which counteracts a tendency of the trailer vehicle (2) to tilt laterally, and the brake light (19) or emergency brake light at the trailer vehicle (2) is actuated as a function of said braking value in such a way that this brake light (19) or emergency brake light signals an emergency braking operation in response to this actuation operation.
 11. A light system for signaling a braking process at a trailer vehicle (2) having the light system and having at least one brake light (19) and having a control device (9) as claimed in one of claims 6 to 10, by means of which this brake light (19) can be actuated.
 12. The light system as claimed in claim 11, characterized by a databus (18) by means of which signals or data can be transmitted from a towing vehicle (1) towing the trailer vehicle (2) to said trailer vehicle (2), an output stage by means of which the brake light (19) can be actuated, and optical cabling via which the brake light (19) can be actuated both from the towing vehicle (1) and from the control device (9).
 13. A trailer vehicle brake installation having an electronic brake system (EBS), having a control device (9) as claimed in one of claims 6 to 10, having at least one brake activation control module (7) which is connected in a signal-transmitting fashion to the control device (9) and having at least one brake activation device (4) which is connected electrically, pneumatically or hydraulically to the brake activation control module (7) and by means of which at least one wheel (3), assigned to this brake activation device (4), of a trailer vehicle (2) having the trailer vehicle brake installation can be braked in response to at least one electrical signal received at the control device (9) or data received at the control device (9), wherein the control device (9) has an interface with a databus (18) through which the signals or data transmitted by a towing vehicle (1) towing the trailer vehicle (2) can be received.
 14. A trailer vehicle having a control device (9) as claimed in one of claims 6 to 10 and/or having a light system as claimed in claim 11 or 12 and/or having a trailer vehicle brake installation as claimed in claim 13 and/or having devices by means of which the method as claimed in one of claims 1 to 5 can be carried out. 